Laser technology continues to make inroads in dentistry. As costs come down and applications for lasers spread—and as pre-doctoral students are increasingly exposed to this technology—expect clinical usage to grow.

Approved for use in dentistry by the US Food and Drug Administration nearly 30 years ago, lasers are available today in a wide array of formats to support many basic dental procedures. Yet, even though there are no restrictions for dentists using lasers and, in most states, no required training,1 it is roughly estimated that only about 20% of US dentists are using laser technologies.

Initially, cost was a stumbling block to dentists acquiring lasers. Over the past 5 years, however, the price range of diode lasers has dipped to $3,000 to $5,000 thanks to strong competition among manufacturers, although the inclusion of higher priced disposable tips has helped these companies recoup some of the discounts. The 10.6-µm CO2 lasers (for soft tissue) are becoming slightly more affordable. Originally in the $40,000 to $50,000 range, some can now be purchased for around $25,000. Erbium lasers remain approximately $40,000 to $60,000, depending on added features.

Dentistry is fast becoming a virtual technology profession. In order to scan tooth preparations effectively, clinicians need sites to be free of bleeding and soft-tissue increments. Lasers can effectively provide this. They also support most surgical procedures due to their excellent photothermal (heat-producing) cutting qualities and hemostatic capabilities. The use of lasers for periodontally supported therapies is on the rise,2 although most dental schools would like to see more university-based research to support this use. In respect to laser perio-supported therapies, the practitioner should have knowledge and understanding of temperature gradients necessary to kill these pathogens.

With roughly 5,000 young doctors graduating each year with little or no training in lasers,3 increased exposure of pre-doctoral students to this technology would surely heighten laser usage. Many students graduate with mountains of college debt, therefore the more affordable diode laser would appear to be an appropriate choice.

Variations of Lasers

The basic laser groups are those that absorb pigmentation and those that absorb water. Regarding pigment absorbers, diode lasers fall into the electromagnetic spectrum at the 808-nm to 1064-nm range. This is invisible infrared (IR) light. Diode lasers have a very low coefficient of absorption for pigmentation.4 In order to use this laser as a cutting tool, it must be converted to a “hot tip” instrument, which is accomplished by carbonizing the tip; all of the laser photon energy stops at the tip. The thermal temperature can reach 500°C or greater. This demands a technique by the operator that will minimize thermal collateral damage to adjacent tissues.

For periodontal therapy, pure laser photon energy should emit from the tip. Ideally, a maximum temperature of 100°C should be achieved. Periodontal pathogens can be killed in the following manners5,6: First, it can be done by denaturation of bacterial cell walls and membranes at 60°C to 80°C. Second, it can occur by pure laser thermal photon absorption by the pigment, which could be termed photothermal lysis. The pigment absorbing the photons should bring the temperature up to 100°C because bacteria are mostly water. The third way is via thermal heat generated by coagulum adhering to the laser tip. Ideally this is done at a minimum compared to the other two components. Too much thermal heat in the periodontal sulcus can lead to collateral damage. Not all pockets are the same; different volumes of chromophore can be present. Thus, 0.6 watts of energy can have multiple effects.

Diode lasers are excellent coagulators.7 Because the energy is not confined in the spatial parameters of the blood vessels, the clinician must work fast. Application technique is critical. Accurately providing de-epithelialization is virtually impossible. Epithelium is only 100 to 300 microns in thickness. Only 5% of diode energy gets absorbed by the epithelium, and 95% is absorbed into the submucosa with penetration depth up to 10 mm. Energy extending greater than 200 to 500 microns can cause thermal damage.8 Necrosis can occur with longer healing times.

A new generation of diode technology, called thermo-optically powered (TOP), utilizes a computer-controlled semiconductor laser as its power source. As with all diode instruments, it is a contact laser. The tip is composed of quartz glass fibers integrated with sintered carbon. A regulating mechanism ensures constant tip temperature. Contrary to traditional diodes, speed control is not a factor in energy application. Operator technique is simplified. The effects are supposedly similar to energy produced by the super-pulsed 10.6 CO2 lasers.8

As diode laser technology has changed, so has CO2 10,600-nm technology. Originally, CO2 lasers were continuous-wave lasers. They had a very high absorption of both hydroxyl-apatite and water and had the potential to generate excessive amounts of heat, which would lead to bone necrosis and collateral tissue damage. The new generation of CO2 lasers operate in the super-pulsed mode, which works as follows9: The rate at how quickly irradiated tissue diffuses heat away is defined by thermal relaxation time. The most efficient heating of irradiated tissue takes place when the laser pulse energy is high and its pulse duration is much shorter than the thermal relaxation time. The most efficient cooling of the tissue adjacent to the ablation zone takes place if the time between pulses (pulse spacing) is greater than the thermal relaxation time.

Adding the dynamics of the super-pulse laser to a CO2 laser, which is an ideal coagulator due to its spatial comparison to blood vessels, creates a highly effective tool. Blood vessels have a diameter of 20 to 40 microns, and photocoagulation of the 10.6 CO2 is 50 microns.10 This makes it a spatial fit, thus minimizing any chance of thermal collateral damage. Work is done in milliseconds and ablation is achieved with simultaneous coagulation. An extremely small volume of irradiated tissue is removed per pulse. Recent published work by Cobb has given hope that the 10.6 CO2 laser may provide a predictable method for surface (titanium implant) decontamination in the treatment of peri-implantitis.11 Results of this work were promising, and the question is whether this can be taken to in vivo studies.

The 9.3-µm CO2 laser recently hit the market. Using sophisticated technology, this laser allows hard tissue to be cut safely and efficiently, and it is projected to cut soft tissue as well.

With erbium lasers (free-running pulse lasers) there are two wavelengths: Er:YAG 2940 nm and YSGG (Er:Cr:YSGG) 2790. This class of laser is primarily being used for ablation of hard tissues. The laser’s absorption chromophore is water. Coolants must be used when ablating hard tissue. The laser does not cut the hard tissue; it searches out water in each hard-tissue component, brings the temperature up to 100°C, and causes microexplosions of the mineralized tissue. Due to its poor photocoagulation depth, the erbium laser is a poor coagulator. It has 20% the efficiency of CO2 lasers.4 Protocols are being developed for the use of erbium lasers in supporting periodontal therapies, including peri-implantitis, although more university studies are needed to support this.

The Nd:YAG laser (also free-running pulsed) has been used in dentistry for many years. It is a pigment absorption laser. Presently, it is being used with a prioritized periodontal protocol (LANAP®).

Emerging Areas

A recent breakthrough has come in the area of photo-acoustics. The PIPS (photon-induced photo-acoustic streaming) process has been shown to be very effective in supporting endodontic therapy.12

The use of lower level laser technologies (LLLTs) is also a new and emerging area.13 This differs from the photothermal laser in that heat is not generated. Photothermal energy breaks down tissue. LLLT lasers utilize multiple wavelengths, ranging from visible 680 nm through invisible 808 nm. This synergistic use of wavelengths provides pain relief as well as reduces inflammation. Photomedicine is a drug-free, non-invasive mode of therapy. Employing a simple biology that involves getting oxygen back into the system through use of red light, some applications of LLLT therapy are treatment of oral mucositis, temporomandibular dysfunction, and improved healing of tissue after surgery.

Finally, fluorescent technologies are being used for oral soft-tissue and caries assessments. The laser for soft tissue is in the 500-nm range and can stimulate certain chemicals (fluorophores) to provide immediate feedback.14 A longer wavelength of light is reflected back (color change) if dysplastic tissue changes are occurring.

In conclusion, expect dental laser technologies to continue to improve while decreasing in price, thereby becoming available to more doctors. The training of pre-doctoral students will aid in the growth and implementation of lasers.